Field of the Invention
The present invention relates to a technique for reducing fixed-pattern noise included in a group of images constituted by a plurality of images (for example, a plurality of images photographed by changing focusing positions, or moving image data) to enhance image quality.
Description of the Related Art
Techniques are known in which an arbitrary viewpoint image or an arbitrary out-of-focus image is generated, through restoration of a light beam space, from a group of a plurality of images that are obtained through an imaging optical system of a camera, a microscope, etc. photographing an object by changing focusing positions (such an image group is hereinafter referred to as an out-of-focus image group). For example, Japanese Patent Application Laid-open No. 2007-128009 discloses a method of generating an arbitrary viewpoint image or an arbitrary out-of-focus image by performing a coordinate transformation process of each image so that the image matches a three-dimensional convolution model and performing a three-dimensional filtering process for changing a blur on a three-dimensional frequency space. Also in documents other than Japanese Patent Application Laid-open No. 2007-128009, methods are proposed for generating an arbitrary viewpoint image or an arbitrary out-of-focus image by restoring a light beam space through a filtering process carried out on integral images of an out-of-focus image group in a viewpoint direction, using formulae that are approximately equivalent mathematically. In the present specification, image generation methods in which an arbitrary viewpoint image or an arbitrary out-of-focus image is generated from an out-of-focus image group through restoration of a light beam space will be collectively referred to as “filter type methods”.
By applying such filter type methods to an out-of-focus image group having been photographed with a camera, a microscope, or the like, functions conventionally unavailable can be provided by means of post-processing after photography, without having to alter an optical system of the camera or the microscope. For example, in the case of a camera, a new way of enjoying photographs can be provided where it is possible to change a blur quality after photography. In the case of a microscope, a stereoscopic shape of an object can be intuitively discerned by changing a point of view. In addition, during high-magnification observation using a lens with a large numerical aperture, increasing a depth of field can prevent a lesion outside of a focusing position from being overlooked.